Fully coupled CFD simulation of the pyrolysis of non-charring polymers: A predictive approach

Abstract

The predictive capabilities of the pyrolysis model implemented in the IRSN ISIS fire simulation software are investigated in the present paper. Cone calorimeter experiments under neutral and usual atmosphere on non-charring polymers, namely PMMA, HIPS and HDPE, are compared to numerical simulations. The pyrolysis and CFD models are chosen to be sufficiently accurate without requiring a posteriori additional parameters fitting. The simulations of gasification experiments are firstly carried out using the pyrolysis model separately with a fixed heat flux as boundary condition, which only requires thermal and thermokinetic parameters that have been fully described in the literature. Predictive simulations of cone calorimeter experiments in flaming conditions need the additional description of the flame feedback flux which is simulated by the CFD model including mass transport, convective and radiative heat transfers and turbulent combustion in RANS framework. In this purpose, the ill-known constants involved in the turbulent combustion model are preliminary calibrated by comparison to the Mc Caffrey diffusion flames reference test case.Both gasification and cone calorimeter simulations provide results in good agreement with their experimental counterparts in terms of mass loss rate and heat release rate evolution, respectively. The analysis of the flame structure resulting from the simulations also suggests that forced pyrolysis performed under cone calorimeter induces larger (and partially laminar) flames than in self-sustained pyrolysis tests, which leads to the preponderance of the radiative effects on the feedback flux.